Really good stuff - voice acting brought me into it. Took me a minute to realize the cards were calculated prior to the opponent's attack, but I might not be the smartest of the bulbs. :D
One thought: I would love to try a version of this game where half the slots get applied before the opponent's attack, and the other half get applied after (or maybe 3 before, 1 after?) - that'd kick the strategy up even higher.
Really good mechanics :)